1. Field of the Invention
The present invention relates to a method of manufacturing an interconnection member and an electronic device, and an interconnection member, multilayered interconnections, an electronic device, electronic device array and a display device using the method.
2. Description of the Related Art
In the related art, photolithography is used to form interconnections, electrodes or the like used in a semiconductor device, an electronic circuit or the like. Photolithography may require expensive equipment since exposure equipment having high accuracy represented by a vacuum device or a stepper is used. Further, the processes may be complicated, the number of processes may be numerous, also the efficiency of utilization of material may be low, and therefore, the manufacturing costs may be high. Thus, photolithography may involve problems.
As a method of reducing the manufacturing costs, a printed electronics technique attracts attention. This is a technique of forming an electrically conductive pattern by directly printing with a functional ink or paste represented by metal fine particles on a base material. Methods of using various printing methods have been proposed therefor.
As a specific example of the printed electronics technology, a patterning method using an inkjet method (liquid droplet discharging method) may be cited. This is a method of directly coating a substrate with a liquid (ink), in which fine particles are dispersed, by an inkjet method, after that, carrying out a curing process by a heat treatment or laser light irradiation, and thus, forming an electrically conductive film pattern. This method is advantageous in that the processes are simplified, also the efficiency of utilization of material is improved, such a material used only for patterning as photoresist used in photolithography is not needed, and the manufacturing costs can be reduced.
However, in an inkjet method in the related art, since discharged liquid droplets may spread after they land, it may be difficult to form a fine pattern, and thus, it may be difficult to respond to a recent request to increase the density of devices, and increase the density and/or miniaturization of interconnections and/or electrodes therefor.
Further, it has been known that in an inkjet method in the related art, a so-called “coffee stain phenomenon” may occur in which a pattern edge part becomes thicker than a pattern center part. Therefore, there may be a problem in which an insulation failure occurs when multilayered interconnections are formed with an upper layer via an insulating film or an electrode of a thin film transistor is formed in an upper layer via a gate insulating film.
In order to solve the problems, various studies have been carried out.
Japanese Laid-Open Patent Application No. 2005-012181 (Patent reference No. 1) discusses a method of providing a bank for defining an area to form an interconnection, and increasing hydrophilicity of a substrate surface part which will be coated with a functional liquid while carrying out a water repellent finish on the bank surface. According to this method, the functional liquid including an interconnection pattern ink is discharged to the area enclosed by the bank and having the increased hydrophilicity, and thus, it is possible to form an interconnection pattern having a width narrower than a diameter of the discharged ink droplet.
However, in this method, many processes may be needed such as a bank forming process, a hydrophilicity increasing process, a water repellency providing process, and so forth. Further, also a vacuum process may be needed. Thus, the advantageous effect of reducing the number of processes of an inkjet method may be lost.
On the other hand, Japanese Laid-Open Patent Application No. 2006-163418 (Patent reference No. 2) and Japanese Laid-Open Patent Application No. 2009-105413 (Patent reference No. 3) discuss methods of forming a depression part having a shape of an electrically conductive pattern in a base member by a laser ablation method or etching, coating the depression part with an electrically conductive material and thus, forming the electrically conductive pattern, or thus forming a thin film transistor.
However, when the depression part is formed by etching, it may be difficult to form a fine pattern since line width and depth are controlled by controlling a liquid dropping amount and a surface treatment. Further, since wet etching is used, this method may have a problem in the efficiency and/or the pattern controllability.
On the other hand, in a case where the depression part is formed by a laser ablation method, it is possible to obtain a width of the depression part thus formed, from a wide pattern through a fine pattern, and the efficiency is relatively high. However, in a case where a laser ablation method is used to work a base material made of a plastic substrate or an insulating film, and a surface treatment is carried out, a residue may be generated on the surface of the base member. Further, concerning depth control in a laser ablation method, since pulsed laser light is used for scanning, a variation may occur in depth, and thus, depth control may involve a problem.
The inventors of the present patent application and so forth previously proposed in Japanese Laid-Open Patent Application No. 2005-310962 (Patent reference No. 4) a laminated structure for which a printing method can be applied and a fine pattern can be easily formed, using a wettability changing material in which critical surface tension is changed by giving energy thereto. In the technology of Patent reference No. 4, first a high surface energy area and a low surface energy area are formed by carrying out one-shot exposure using a photo mask on a wettability changing layer on a substrate surface. Next, a pattern is formed by dropping a hydrophilic ink on the high surface energy area by an inkjet method. In this method, it is possible to form a fine pattern merely by adding a single exposure process in comparison to an ordinary inkjet printing. However, in this method, since a surface to form an electrically conductive pattern is approximately a flat surface, a defect may be generated in an electrically conductive pattern in a case of forming a very fine pattern, and thus, a further improvement may be needed.
Further, Japanese Laid-Open Patent Application No. 2009-026901 (Patent reference No. 5) discusses that a depression part is formed by a reduction in film thickness by 5 nm or more, 10% or less of the film thickness of a wettability controlling film through ultraviolet irradiation. However, a change in surface energy and the depth of the depression part are controlled by controlling an ultraviolet irradiation amount. Therefore, it may be difficult to control both the surface energy and the depth of the depression part to the respective target values simultaneously, since the surface energy may be changed on the order of the target amount merely by irradiation of a small amount of ultraviolet rays whereas a long time of ultraviolet irradiation is needed to form a deep depression part.